The present invention relates to remote electrical switches and particularly to those using a fusible material or a eutectic to bridge a gap between a pair of spaced electrical contacts. Also, the present invention relates to a switch having magnetic means for moving an element bridging such contacts.
The use of a fusible element or eutectic in such switches devices as fues is well known to the art. For example, Zankl, U.S. Pat. No. 3,947,798 shows a fusible element forming part of an electrical path. After the fusible element melts, it is moved by the force of gavity, thereby opening the electrical path. Other switches or fuses employ a fusible element in combination with mechanical urging means to bias a separate element held in position by the fusible material. See, for example U.S. Pat. Nos. 3,964,010, 3,043,937 and 2,599,411.
Still other types of switches or fuses known to the art include magnetic means which use a Lorentz force to move a liqiud element through which current is passing. For example, Rabinowitz et al, U.S. Pat. No. 3,462,573 shows a circuit interrupter using liquid gallium disposed in a container having opposing ends, one of such ends being positioned within the field of an electromagnet. Means are provided to pass current through the liquid, and when a magnetic field is applied, the Lorentz force moves the liquid out of the field, thereby opening the electrical path.
Several disadvantages inhere in the prior art switches or fuses. Those using a eutectic or fusible material are generally not reusable. Others such as Zankl are reusable but must be manually reset. Accordingly, while they may be remotely positioned, they must be accessable to a manual operator for resetting purposes.
Switches such as Rabinowitz using liqiud elements such as liquid gallium or mercury are position sensitive and interpose a significant resistance with the switch is in closed position. Hence, such a switch is disadvantagious where residual contact resistance is a major factor, such as in remote selection of one of a plurality of resistances or voltages to be applied to an electrical circuit.
Accordingly, it is the principal object of the present invention to provide a switch which has an extremely low closed resistance.
It is a further object of the present invention to provide a reusable switch which may be operated from a remote position.